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A reconfigurable mesh of silicon Mach-Zehnder Interferometers (MZIs) is employed to manipulate optical beams in order to establish free-space optical communication channels. Automated feedback-control strategies enable the mesh to self-calibrate and maintain the transmission quality in presence of perturbations of the beam front.

We present a novel design for a reconfigurable silicon microring resonator filter exploiting non-integer Vernier ratio to achieve FSR-free spectral response. Hitless tunability across the extended C+L band (1520 nm-1620 nm) is achieved by introducing controllable loss in the MRRs of the filter.

The increasing requirements in terms of bandwidth and power efficiency demanded by telecommunication, automotive and datacenter applications are pushing copper-based interconnections close to their intrinsic limits [1]. On the same line, the emerging trends on new rack-scale multi-socket computational units are putting pressure on chip-to-chip interconnections, calling for high speed and low-latency performance at a reduced energy and cost [2]. These technological requirements are making copper-based interconnects the bottleneck of high-performance systems, suggesting the use of point-to-point optical connectivity not only for long range communications but also at short or ultra-short distances [3]. With respect to other solid-state solutions, Silicon Photonics (SiP) seems to be the ideal candidate to answer to these needs, as it shares the same fabrication technologies of the microelectronic industry and is therefore expected to play a significant role in the field.

A reconfigurable mesh of silicon photonic Mach-Zehnder Interferometers to manipulate free-space optical beams is presented. We demonstrate beam steering, beam coupling from free-space optical source into a single mode waveguide and automatic identification of the direction of arrival of a beam from a free-space source.

Thermal cross-talk can impair the efficiency of tuning algorithms employed for the control, calibration and reconfiguration of photonic integrated circuits (PICs). For example, in coupled microring resonator (MRRs) architectures, thermal crosstalk is responsible for an unwanted coupling among the round-trip phases of the resonators, thus affecting their resonance frequencies. Here we propose a novel approach, named Transform Coordinate method (TCM), enabling thermal cross-talk cancellation in PICs. In the TCM, instead of controlling the phase shift of each photonic element individually, the eigensolutions of the thermally coupled system are calculated and employed as control variables. The effectiveness of the TCM is demonstrated by implementing a feedback control system providing automatic resonance tuning of 3rd order coupled MRR filters. Numerical simulations, confirmed by experimental results achieved on a high-index-contrast silicon oxynitride (SiON) platform, demonstrate that the TCM enables a tuning process that is faster, more accurate and more robust with respect to conventional methods based on individual tuning of each MRR. Further, the TCM can be used as a wavelength locking algorithm to maintain the tuned condition in the presence of temperature drift as well as random fluctuations of the wavelength and of the power of the input signal. Finally, the TCM can be applied to generic PIC architectures based on arbitrary combinations of MRRs and other integrated interferometric devices.

Silicon oxycarbide thin films deposited with reactive rf magnetron sputtering are exploited to fabricate photonics waveguides with two high refractive indices of 1.58 and 1.82 exhibiting index contrast of 8% and 18% with silica glass. The propagation losses are estimated in the telecom wavelength range and the results demonstrate the potential of silicon oxycarbide for photonics applications.

We propose and demonstrate a photonic integrated circuit performing simultaneous mode and wavelength demultiplexing. The circuit can receive up to two fibre modes and four wavelength channels per mode. The mode demultiplexing stage integrates a reconfigurable linear network for all-optical MIMO processing, enabling the unscrambling of the mode mixing generated by fibre propagation.

We demonstrate the application of several stochastic tools to the design of photonic integrated circuit. Monte Carlo analysis based on real measured statistics of the parameters is used to investigate of the impact of fabrication tolerances on the performance of a switch, including average power required for trimming. Polynomial-chaos-based models are used to optimize a filter design in order to minimize fluctuations of the bandwidth due to fabrication uncertainty. Sensitivity analysis performed through elementary effect test and variance based approach is used to identify the most critical parameters determining bandwidth fluctuations.

In recent years, silicon photonics has attracted attention as an emerging technology for optical telecommunications and for optical interconnects in microelectronics. The refractive index contrast plays a fundamental role in determining the characteristics of an optical dielectric waveguide and a higher index contrast permits to move towards larger scales of integration and to access new devices and functionalities. But high contrast waveguides are more difficult to realize and more critical but there are no serious impediments in their use. The aim of this contribution is to investigate the dependence of the waveguide characteristics with respect to the index contrast and explore the difficulties. In this paper, the impact of the index contrast on the characteristics of dielectric waveguides such as single mode regime, losses, fiber to waveguide coupling, technological constraints and available materials are investigated. The investigation shows that the dependence of the sensitivity in optical waveguide sensors on the polarization of guided modes is less in small refractive index difference waveguide compare than the silicon on silica waveguides but it provide flexibility to the design engineers.

We present a control system for wavelength stabilization of silicon MRR used to improve ER in a four-channel DML-based transmitter. The ER enhancement is achieved with automatic control and the sensitivity of the system is better than −28 dBm at 10−3 BER after 40-km transmission.

In this work, we present integrated photonic sensor design to detect Chemical, Biological, Radiological and Nuclear (CBRN) threats, where high sensitivity and no false positive are strictly required. The sensor is formed by several parallel micro-ring resonators exposed to the environment and functionalized to recognized target analytes in a free-label way. Experimental demonstration of the working principle was performed using simulant compounds that permit tests of the features of the Photonic Integrated Circuit (PIC) in a safe environment. The results show the possibility of using PICs to detect as low as 20 ppb of Ovalbumin (simulant for Ricin A toxin) and 200 CFU/ml of Bacillus cereus spores (simulant for Bacillus anthracis). These results push forward the possibility of using PICs as biochemical sensors, also for critical objectives.

InP and Silicon Photonics integrated optical devices able to mux and demux signals encoded on different orthogonal modes. They operate on 2 and 4 channels at 10 Gbit/s with less than −15 dB residual crosstalk. Transparent photodetectors, realized though the non-invasive ContacLess Integrated Photonic Probe (CLIPP) technology are exploited to assist the (de)mux configuration.

We present an L-band WDM transmitter exploiting a feedback-controlled Si photonic circuit for channel multiplexing and extinction ratio enhancement of four DML sources. 4×10 Gbit/s transmission along a 50-km SMF is demonstrated.

A 32channel electronic system for non-invasive light monitoring in integrated photonic circuits with contactless waveguide conductance detector (CLIPP) is presented, featuring 10pS resolution to address multipoint tuning and controlling of optical power variations below −30dBm.

Nowadays, multimedia objects can be easily modified, shared, and distributed, thus determining the widespread diffusion of multiple near-duplicate versions, i.e., objects obtained applying a set of processing operations to original content. This is the case of images downloaded from sharing platforms, modified (e.g., by performing color correction, splicing, etc.) and re-distributed. The evolution of a group of near-duplicate images (i.e., their phylogeny) is a powerful clue to determine both image authenticity and its origin. For this reason, the forensics community has proposed a set of possible solutions to perform phylogenetic analyses based on image dissimilarity computation. Here, we compare different image dissimilarity metrics, and propose a set of original strategies for image phylogeny tree reconstruction. The validation of the proposed methods is performed on a dataset of image phylogeny trees. Depending on the used evaluation metrics, some approaches are preferable to others according to the results. Hence, an analyst can choose the appropriate method according to its needs.

A novel silicon photonics filter enabling single-channel-extraction over a wavelength range wider than the telecom C-band is proposed. An extraction bandwidth of only 15 GHz is demonstrated with off-band rejection of more than 15 dB.

We demonstrate feedback-control of a thermally actuated silicon microring resonator integrating a transparent light monitor. The microring resonance is locked to the wavelength of an external laser with 150 ms time response.

A high sensitivity in-band OSNR monitor system integrated on SOI platform is presented. The device exploits a narrow-band microring resonator to select the portion of the channel spectrum that is most sensitive to OSNR variations, and performs an autocorrelation measurement using a Mach-Zehnder interferometer. The proposed scheme allows in-line OSNR monitoring from 8 dB to 28 dB, with 0.2 dB accuracy.

We present results on optical crosstalk in the photonic integration platform developed at Fraunhofer HHI. Two fundamental mechanisms are investigated: stray light generation at butt-joints and coupling between two passive waveguides. The latter can happen in two regimes: evanescently or radiatively, depending on the gap between the waveguides. Measurements show the amount of crosstalk that is to be expected on ASPICs. Moreover, means to reduce crosstalk levels that are compatible with the existing technology are demonstrated.

Non-invasive monitoring of silicon microring resonators is demonstrated through a novel contactless integrated photonic probe, which enables multi-point light observation on chip and proves its utility for the tuning and control of photonic integrated devices.

Single fiber to silicon waveguide automated coupling is demonstrated by using a fully CMOS-compatible transparent light probe integrated near the chip edge. Fast feedback-loop alignment (15 s) is achieved with no need for external photodetector.

The use of architectures that implement optical switching without any need of optoelectronic conversion allows us to overcome the limits imposed by today's electronic backplane, such as power consumption and dissipation, as well as power supply and footprint requirements. We propose a ring-resonator based optical backplanes for router line-card interconnections. In particular we investigate how the feasibility of the architecture is affected by the following parameters: number of line cards, switching-element round-trip losses, frequency drifting due to thermal variations and waveguide-crossing effects. Moreover, to quantify the signal distortions introduced by filtering operations, the noiseless eye diagrams for the different parameter conditions are shown in case of an on-off keying non-return-to-zero input signal at 10 Gb/s.

Optical carrier reduction via the use of a Si 3 N 4 ring resonator notch filter (RRNF) is proposed and experimentally demonstrated for improving the modulation efficiency in a 10 GHz radio-over-fiber (RoF) system.

Sandwiching a photosensitive layer of As2S3 between Si core and polymer cladding enables trimming of athermal waveguides. Moreover, athermal operation enables the compensation of thermal effects related to Si nonlinearity with respect to standard waveguides.

Building block and circuit simulation concepts are discussed with their advantages for the design and the production of photonics integrated circuits. Two examples are presented to demonstrate the validity of the circuit-based simulation in the prediction of the behaviour of the real circuit. Final results are comparable to those obtained through an electromagnetic simulation, also when spurious effects as mode coupling or chip facet induced cavities are taken into account.

In this contribution we present a new and efficient technique for post-fabrication trimming of chalcogenide (ChG) based photonic integrated circuits (PICs). The technique exploits the high photosensitivity of As 2 S 3 glass to visible light radiation in order to induce a variation in the refractive index of the material, and therefore in the optical properties of ChG-based devices. The trimming technique enables not only to compensate for fabrication tolerances and restore desired functionalities, but also to provide a tool for the reconfiguration of photonic circuits. We demonstrate the trimming of PICs employing As 2 S 3 core waveguides and As 2 S 3 -assisted silicon waveguides. Finally, to further show the wide versatility of this approach, we apply the technique to trim the response of As 3 S 3 silicon waveguides covered with an additional polymer cladding layer, demonstrating simultaneous athermal operation and trimming functionality.

We demonstrate that travelling-wave four-wave mixing in coupled resonators overcomes the bandwidth limitations of wavelength conversion in single resonators, preserving the efficiency enhancement: 28-dB gain over silicon waveguides of the same length is here achieved.

Visible light trimming of As 2 S 3 -assisted optical waveguides is exploited to compensate for fabrication tolerances and to demonstrate permanent reconfiguration of photonic integrated circuits. Applications to ring-resonator filters and variable delay lines are presented.

We discuss here the potential of compact ring-based high-order photonic integrated filters. Limitations related to fabrication tolerances and parasitic effects in high-index-contrast waveguides are also addressed and adaptive tuning of the filter parameters is proposed and demonstrated as a viable compensation strategy to maintain filter operation.

In silicon (SOI) waveguides, two-photon absorption (TPA) and free-carrier absorption (FCA) in the 1550-nm wavelength range are responsible for an intensity-dependent extra-loss and refractive index change. Recombination of the free carriers generated by TPA produces a local heating of the waveguide [1] depending on the local optical power which causes an increase of the refractive index and alters the behaviour of multi-stage circuits because the power level can change locally, especially inside optical resonators where the intracavity power is enhanced according to the cavity finesse.

Silicon-on-insulator (SOI) micro-ring resonator (RRs) demonstrated to be a versatile building block to realize integrated optical filters for several telecom and sensing applications, providing unique features in terms of large bandwidth, footprint reduction and quality factor enhancement. Demanding spectral specifications, such as sharp pass-band transitions, can be achieved with higher order filters made by suitably cascading multiple RRs [1]. However, the high index contrast of SOI platform makes these devices very sensitive also to small inaccuracies in the fabrication process. This produces, even with a state-of-the-art technology, a spectral spreading of the resonance positions, which quickly deteriorates the response of the filter. An accurate control of the resonance frequencies is therefore a challenging issue, which generally requires further fabrication steps, complex algorithms and power consumption techniques [2].

A software platform able to fulfill the requirements of the new approach in photonic integration through the establishment of generic foundries is presented. The kernel is a circuit simulator able to combine the foundry building blocks described by accurate models to design and analyze complex circuits in the spectral domain.

We show a direct comparison between silicon reconfigurable delay lines based on coupled resonator optical waveguides and photonic crystal waveguides. The structures are used to selectively delay the two orthogonally polarized channels of a RZ-PolDM-DQPSK format at 100 Gbit/s.

In ideal conditions the Four Wave Mixing conversion efficiency is enhanced by the slowing down factor to the fourth power. We have investigated FWM in Coupled Resonator Optical Waveguides both numerically and experimentally this phenomena, also in presence of attenuation and chromatic dispersion.

Coupled resonator optical waveguides (CROWs) are widely considered promising building blocks for the on-chip processing of wideband data-streams. The performances of these structures are much sensitive to disorder effects, affecting both losses and the maximum achievable slowing ratio. To date, how and how much disorder influences the slow-wave propagation regime is still an open issue. In this contribution, an analytical model is presented, showing the relation between the back-reflected power due to random variations in the resonant frequencies of the CROW resonators, referred to as phase disorder, and the actual group velocity of the disordered structure. The model can be applied to any CROW, independently of the architecture and technology, and is supported by numerical simulations and experimental results. The effects of an increasing phase disorder were observed in the frequency response of ring-resonator (RR) CROWs, where the resonance frequency of each RR is independently controlled by a thermal activation of the optical waveguide.

Reconfigurable architectures based on bi-dimensional arrays of integrated ring-resonators (RRs), also known as resonant routers (ReRs), are good candidates for implementing advanced routing and switching operations in both WDM and access optical networks. ReRs provide high flexibility, full reconfigurability and the capability of handling many WDM optical channels in small footprint devices. In this contribution, we demonstrate experimentally that the bandwidth of a ReR can be significantly narrowed with respect to the signal bandwidth, while corrupting neither the signal quality nor the crosstalk between routed channels. To this aim, a small frequency detuning between the signal carrier and the ReRpsilas frequency response is introduced. In this condition, the frequency chirp provided by the RRs dispersion can also be exploited to make the transmitted signals more robust against fiber chromatic dispersion. The routing of two intensity modulated 2.5 Gbit/s and 10 Gbit/s NRZ channels through a 2times2 integrated ReR with 4 GHz bandwidth is reported and the signal quality after propagation through several spans of optical fiber is evaluated.

Continuously tunable relative delay between orthogonally polarized data-streams is demonstrated in an integrated ring-resonator CROW. System performance and applications to polarization-division multiplexing transmission systems are discussed.

A continuously tunable delay of 8 bit-lengths at 10 and 25 Gbit/s is achieved by using a ring-based coupled-resonator-optical-waveguide fabricated in SiON technology. Fractional loss below 1 dB per bit-delay and storage efficiencies exceeding 1 bit-delay per ring-resonator are demonstrated.

In this contribution the potentialities and the limitation of the silicon oxynitride (SiON) technology are reviewed and a number of integrated optical circuits and devices are presented. Mach-Zehnder, ring resonators, variable bandwidth filters, ring resonators based cross-bar matrices and a DQPSK receiver with interleaver and variable attenuators have been realized, characterized and tested in a 10 Gbit/s WDM system.

This study investigates a bent waveguide by modelling its polarization rotation. The work shows that the process of polarization conversion in the bend is dependent on the straight waveguide characteristics

The Resonant Router (ReR) is an integrated optics crossbar matrix based on ring resonators. Depending on the characteristics of the rings the ReR can operate as cross-connect (X-ReR) or as wavelength router (?-ReR). The analysis of the device, the spectral characteristics and the impact on a high bit rate signal are presented and discussed both on theoretical and experimental basis. The ReR can add flexibility and extend the capabilities of a node of a transparent optical network.

A slow-wave structure (SWS) consists of a series of directly-coupled Fabry-Perot or micro-ring resonators, in which light can propagate only at certain frequencies in a band around the resonances of the structure. In the case of pulse propagation, the interplay of nonlinearity and anomalous dispersion can be deployed to make solitary waves propagate undistorted along an high number of resonators. It is possible to significantly enhance nonlinear phase modulation by exploiting the slowing down of the optical propagation as well as to deploy the SWS spectral response to generate SPM based nonlinear effects which can have interesting application in the field of the optical processing.

A very compact integrated optical device, including a pair of two-arm Mach-Zehnder interferometers realized in silicon oxynitride technology (SiON), is proposed as a receiver for optical DQPSK transmission systems. A review on high-index contrast SiON technology is given with details on the design, technological realization and optical characterization of the presented device. System measurements, including BER curves, are reported to show the performance of the receiver in a RZ-DQPSK system operating at 10 Gsymbol/s. To reduce impairments due to the frequency mismatch between receiver and transmitter, a dynamic thermal tuning of the receiver has been realized and its contribution to system's penalty reduction is experimentally demonstrated.

The impact of ring-resonator filters on optical signals and system performance is investigated. Pulse-shape distortions and system penalties induced by a single-ring and a double-ring filter are calculated and measured. The filter cascadability, in the presence of detuning and birefringence too, is theoretically investigated. Experimental results on the system Q-factor and BER measurements carried out on optical communication NRZ systems at 2.5 Gbit/s and 10 Gbit/s are reported and discussed.

The linear and nonlinear characteristics of waveguiding structures made of direct-coupled Fabry-Perot or ring resonators are investigated. It is shown that the slowing down of the optical propagation in these structures may be advantageously exploited to enhance wave interactions.

The resonant router (ReR) is an integrated optics crossbar matrix based on ring resonators. Depending on the characteristics of the rings the ReR can operate as cross-connect (X-ReR) or as wavelength router (/spl lambda/-ReR). The analysis of the device, the spectral characteristics and the impact on a high bit rate signal are presented and discussed both on a theoretical and experimental basis. The ReR can add flexibility and extend the capabilities of a node of a transparent optical network.

The Resonant Router (ReR) is an integrated optical crossbar matrix based on the ring resonator. The ReR can operate as cross connect or wavelength router depending on the FSR and bandwidth of each node. In this contribution the cross connect characteristics are investigated, focusing on the characteristics of the single nodes, the necessaries technologies and the impact on WDM systems. An effective method for the BER estimation of the ReR is presented.